Tunable lens device

ABSTRACT

An actuator including an electrically conducting coil arranged on or integrated into a wall member, wherein the electrically conducting coil is arranged adjacent to a magnetic flux return structure. A magnet connected to a carrier, wherein the magnet interacts with the electrically conducting coil such that when a current is applied to the coil the coil is either moved towards the carrier along an axial direction or away from the carrier along the axial direction depending on a direction of the current within the coil. A magnetic flux guiding structure connected to the carrier, wherein magnetic flux is guided through the flux return structure and the flux guiding structure.

REFERENCE TO EARLIER FILED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/821,484, filed Nov. 22, 2017 (pending), which is a continuation ofU.S. application Ser. No. 15/028,150, filed Apr. 8, 2016, now U.S. Pat.No. 9,841,539, which is a 371 national phase of PCT/EP2014/071541, filedOct. 8, 2014, and claims the benefit of priority to European ApplicationNo. 13187802.7, filed Oct. 8, 2013, the entire disclosures of each ofwhich are incorporated herein by reference.

The invention relates to a tunable lens device according to the preambleof claim 1. Further, the invention relates to a method for adjusting alens device as well as for providing image stabilization or light beamdeflection and shaping.

A lens device of the afore-mentioned kind usually comprises atransparent and elastically expandable membrane, an optical elementopposing or facing the membrane, a wall member, wherein the opticalelement and the membrane are connected to the wall member such that avolume is formed, wherein at least the membrane, the optical element,and said wall member delimit said volume (also denoted as container), afluid residing in said volume, and a lens shaping member attached to anoutside of the membrane, which outside faces away from said volume.

Tunable lens devices, especially for image stabilization are known inthe state of the art. US20100295987A1 describes an imaging device wherea liquid lens comprises a liquid-liquid interface between first andsecond immiscible liquids deformable by electro-wetting.

Further, US20110158617A1 discloses an image stabilization device andmethod, wherein actuators act on both sides of a flexible lens, so as totilt one side and to bend the other side.

Furthermore, EP2338072A1 describes an electro-active lens comprising anoptical element being an elastic solid, wherein upon application of avoltage to electrodes of the optical element, the latter is deformed inorder to alter its optical properties.

Based on the above, the problem underlying the present invention is toprovide for a lens device that allows for tuning the focus of the lensdevice as well for adjustments of the light beam direction (e.g. for thepurpose of image stabilization or beam redirecting) in a simple manner.

Further, it is an objective of the present invention to provide for amethod for adjusting a lens device as well as for a method for imagestabilization.

This problem is solved by a lens device having the features of claim 1.

Preferred embodiments of the lens device are stated in the correspondingsub claims and are described below.

According to claim 1, the lens device comprises an actuator means thatis designed to move the optical element in an axial direction withrespect to the lens shaping member (e.g. towards and away from the lensshaping member), so as to adjust the pressure of the fluid residinginside the volume and therewith a curvature of said membrane, whereinsaid axial direction is oriented perpendicular to a plane spanned by thelens shaping member, and/or wherein said actuator means is designed totilt the optical element with respect to said plane, particularly so asto form the volume into a prism for deflecting light travelling throughthe volume.

Particularly, the fluid resides in the volume such that the curvature ofthe membrane can be adjusted by adjusting the pressure (or force)exerted on the membrane (e.g. via the lens shaping member).Particularly, the fluid fills the volume completely.

However, according to an aspect of the present invention (e.g. forautofocus applications) the tilting movement can be an optional feature,e.g. merely a (relative) axial movement between the optical element andlens shaping member is necessary.

Generally, according to an aspect of the present invention, the actuatormeans may rather be designed to move the lens shaping member in an axialdirection with respect to the optical element. Then, said axialdirection is instead oriented perpendicular to a plane along which theoptical element extends (e.g. perpendicular to optical element).Further, the actuator means is then designed to tilt the lens shapingmember with respect to said plane (optical element), particularly so asto form the volume into a prism for deflecting light passing through thevolume.

In this sense, particularly, moving the optical element in an axialdirection with respect to the lens shaping member may also mean arelative movement between these components where for instance theoptical element is at rest and the lens shaping member is moved.Likewise, in this sense, particularly, tilting the optical element withrespect to said plane, particularly so as to form the volume into aprism for deflecting light passing through the volume, may also meanthat the optical element is at rest and said plane (i.e. the lensshaping member) is tilted.

Further, particularly, the notion, that the lens shaping member spans aplane means that the lens shaping member spans or defines a fictitiousplane or extends along such a fictitious (extension) plane. This planebeing particularly a fictitious plane may be used for definingdirections, such as an axial direction running perpendicular to saidplane. Particularly, one may also state that said axial direction runsperpendicular to the lens shaper. In embodiments, where the lens shaperis a circumferential structure said structure or a surface thereofextends in said plane (and thus defines or spans said plane).

Particularly, when the optical element is moved along the axialdirection the lens shaping member presses against the membrane or pullsthe membrane accordingly.

When the lens shaping member presses against the membrane due to themovement of the optical element/wall member towards the fixed lensshaping member, the pressure of the fluid increases due to theessentially constant volume of the fluid causing the membrane to expandand said curvature of the membrane to increase. Likewise when the lensshaping member pushes less against the membrane or even pulls themembrane, the pressure of the fluid decreases causing the membrane tocontract and said curvature of the membrane to decrease.

Increasing curvature thereby means that the membrane may develop a morepronounced convex bulge, or that the membrane changes from a concave ora flat state to a convex one. Likewise, a decreasing curvature meansthat the membrane changes from a pronounced convex state to a lesspronounced convex state or even to a flat or concave state, or changesfrom a flat or concave state to an even more pronounced concave state.

Thus, in other words, the present invention enables autofocus and imagestabilization by deforming a membrane by moving only one componentaxially, here the optical element (or an element such as the wall memberconnected thereto), with respect to the lens shaping member, and bytilting said component, thus providing a tunable prism.

Hence, advantageously, the invention allows for using the same actuatorsthat are used for deforming the membrane also for x-y scanning (allowingfor image stabilization as well as the construction of scanners for beamdeflection), while the membrane can still be attached to a fixed lensshaping element. This also allows for preventing lateral displacement ofthe variable lens surface used for focusing, resulting in better opticalquality of the overall optical system.

When tilting, the actuator means is preferably designed to be controlledsuch that the pressure in the fluid is kept constant, so that thecurvature of the membrane is kept constant upon tilting the wallmember/optical element.

The membrane can be made of at least one of the following materials: aglass, a polymer, an elastomer, a plastic or any other transparent andstretchable or flexible material. For example, the membrane may be madeout of a silicone-based polymer such as poly(dimethylsiloxane) alsoknown as PDMS or a polyester material such as PET or abiaxially-oriented polyethylene terephtalate (e.g. “Mylar”).

Further, the membrane can comprise a coating. Further, the membrane canalso be structured, e.g. comprise a structured surface.

Further, said fluid preferably is or comprises a liquid metal, a gel, aliquid, a gas, or any transparent, absorbing or reflecting materialwhich can be deformed. For example, the fluid may be a silicone oil(e.g. Bis-Phenylpropyl Dimethicone).

Additionally the fluid may include fluorinated polymers such asperfluorinated polyether (PFPE) inert fluid.

Furthermore, the optical element is preferably rigid compared to themembrane.

Preferably, the optical element is formed out of or comprises: a glass,a plastic, a polymer, or a metal. It can comprise or can be formed as a(e.g. glass) flat window, a lens, a mirror, a micro structured elementwith refractive, diffractive and/or reflective structures.

Further, to a preferred embodiment of present invention the opticalelement may comprise a coating (e.g. anti-reflection).

According to a preferred embodiment of the present invention, theactuator means is designed to move the optical element axially and totilt it at the same time. Preferably such that the axial movement andthe tilt movement can be defined as control variables.

According to a preferred embodiment of the present invention, theactuator means is designed to act on the wall member for moving theoptical element axially and for tilting the optical element.Alternatively, the actuator means is designed to act on the lens shapingmember for moving and/or tiling the lens shaping member. Further, in thesense described above, the actuator means may be designed to generate arelative movement between the optical element and the lens shapingmember, where the optical element and the lens shaping member are movedrelative to one another along the axial direction or are tilted withrespect to one another.

According to a preferred embodiment of the present invention, the wallmember is formed by an e.g. rectangular plate having a continuous recess(e.g. in the center of the plate, which recess extends from a first sideof the wall member to a second side of the wall member, which secondside faces away from the first side, wherein preferably the opticalelement is connected to the first side so as to cover said recess, andwherein preferably said membrane is connected to the second side of thewall member.

According to a preferred embodiment of the present invention, the lensshaping member is connected to the wall member, preferably to the secondside of the wall member via a deformable wall. According to anotherpreferred embodiment of the present invention, the lens shaping elementmay be connected to the optical element via a deformable wall.Preferably, the deformable wall then extends through the recess of thewall member/plate to the optical element and therefore delimits saidvolume (instead of the inner side of the recess).

According to a preferred embodiment of the present invention, saiddeformable wall is formed as a bellows.

Preferably, said bellows comprises a plurality of regions, whereinpreferably each two neighboring regions are connected to each other viaa crease, so that said neighboring regions can be folded towards andaway from each other about the respective crease, particularly such thatwhen the optical element is moved/tilted towards the lens shaping membersaid neighboring regions are folded towards each other (at least in aregion where the optical element and the lens shaping member approacheach other), and such that when the optical element is moved/tilted awayfrom the lens shaping member said neighboring regions are folded awayfrom each other (at least in a region where the optical element and thelens shaping member depart from each other).

The creases of the bellows may be structurally reinforced by rigidelongated members.

In a preferred embodiment of the present invention, the bellowscomprises two circumferential regions connected via a singlecircumferential crease of the bellows.

According to a preferred embodiment of the present invention, the lensshaping member delimits an optically active and elastically expandable(e.g. circular) region of the membrane, wherein particularly said regionextends up to an (e.g. circumferential) inner edge of the lens shapingmember, and wherein particularly said region comprises said curvature ofthe membrane to be adjusted.

According to a preferred embodiment of the present invention, the lensshaping member is rigidly connected to a carrier, wherein particularlythe carrier faces the second side of the wall member. Said carrier maycomprise or may be formed by an optical assembly. The optical assemblymay be formed or may comprise an image sensor and/or a lens stack,wherein particularly said lens stack is arranged between the imagesensor (e.g. CCD sensor) and the membrane.

According to a preferred embodiment of the present invention, theactuator means comprises a plurality of electrically conducting coils,particularly at least three coils, or four coils, which are arranged onor integrated into the wall member, particularly along the recess.Preferably, each coil is equally spaced from its two neighboring coilsalong the recess.

According to a preferred embodiment of the present invention, theactuator means comprises a magnet means connected to the carrier.Preferably, said magnet means comprises a plurality of magnets beingconnect to the carrier respectively, wherein each magnet is preferablyassociated to a different coil. Preferably, said magnet means or saidmagnets are designed to interact with said coils such that when acurrent is applied to a coil the respective coil is either moved towardsthe carrier (along said axial direction) or away from the carrier (alongsaid axial direction) depending on the direction of the respectivecurrent. The displacement of the wall member/plate is proportional tothe current.

According to a preferred embodiment of the present invention, a magneticflux guiding structure (e.g. out of a magnetically soft material such ase.g. iron) for shaping the magnetic flux generated by the respectivemagnet is provided for each magnet, wherein each magnetic flux guidingstructure comprises an end region that protrudes through an associatedaperture of the wall member as well as into or through the coilsassociated to the respective magnet. Preferably, the magnetic fluxguiding structures are connected to the carrier, respectively.

According to a further embodiment the actuator means comprises aplurality, particularly, two, three or four, electrically conductingcoils connected to the carrier. Preferably, the coils are each arrangedadjacent to an associated magnetic flux return structure (e.g. out of amagnetically soft material such as e.g. steel).

Further, preferably, the actuator means comprises a correspondingplurality of magnetic flux guiding structures arranged in or on the wallmember, wherein each magnetic flux guiding structure is associated to adifferent coil, and faces or opposes the respective coil/magnetic returnstructure such that a gap is present between the respective returnstructure/coil and associated magnetic flux guiding structure. However,according to a further embodiment, it is also possible that the actuatormeans comprises only a single magnetic flux guiding structure facing oropposing the coils (e.g. the wall member may itself form the magneticflux guiding structure). Further, according to a further embodiment, itis also possible that the actuator means comprises only a single returnstructure adjacent said coils.

When a current now flows through the coils, the magnetic flux is guidedthrough the respective return structure and the respective flux guidingstructure. Since the system wants to reduce the magnetic resistance, therespective magnetic flux guiding structure will be attracted to theassociated return structure to reduce the gap between the twomagnetically soft structures and to reduce the resistance for themagnetic flux. Thus, the wall member and optical element are moved.Depending on the current in the respective coil this allows one to movethe wall member axially along said axial direction and/or to tilt thewall member with respect to the plane spanned by the lens shapingmember. Such an actuator means is also denoted as reluctance actuator.

According to a further embodiment, the actuator means may comprise aplurality of first electrodes, particularly, two, three or four,arranged in or on the wall member, as well as a corresponding pluralityof second electrodes connected to the carrier, wherein each firstelectrode is associated to a different second electrode and faces oropposes the respective second electrode so that a gap is present betweenthe respectively associated electrodes. By applying a voltage betweenthe respective first and second electrodes, the optical element can beaxially moved and or tilted with respect to said plane.

According to a preferred embodiment of the present invention, the lensdevice comprises a position sensor means for detecting the spatialposition of the optical element or of a component connected to theoptical element such as the wall member, e.g. with respect to areference position such as the position of the lens shaping member. Byadjusting the spatial position of the optical element to a definedstate, the optical properties of the lens device can be defined. Thisincludes the optical power of the lens formed by the deformablemembrane, and the angle of the variable prism.

When using an actuator means in the form of a reluctance actuator, theposition sensor means can advantageously be designed to use a highfrequency current signal for measuring the spatial position of the wallmember/optical element via the coils. In other words, in an embodimentof the invention, the actuator means is used to detect the spatialposition of the wall member/optical element, particularly by beingdesigned to directly sense the reluctance of the reluctance actuatorassociated to the gap between the flux guiding structure(s) 740 and thereturn structure(s) 700.

When the wall member moves closer to a coil due to a movement, the gapbetween the coil/return structure and the wall member becomes lesscausing the reluctance of the magnetic field to reduce and thus the coilinductance to increase, which is therefore a measure for the width ofsaid gap and therefore for the spatial position of the wallmember/optical element. The biggest advantage of this method is that itshows a linear relationship between the output signal and thedisplacement (gap width) of the wall member/optical element.

According to a preferred embodiment of the present invention, theoptical element is transparent. In this case the lens device may be apart of a camera or may itself form a camera, for instance a camera of amobile phone.

According to another embodiment of the present invention, the opticalelement is formed as a mirror having a reflecting surface facing e.g.towards said volume. For example, said mirror may be adapted to reflectlight that enters the lens trough the membrane, travels through saidvolume, impinges on the mirror and is then reflected towards themembrane.

In this case the lens device may be a part of a scanner or may itselfform a scanner.

Further, the optical element may comprise a coating.

According to a preferred embodiment of the present invention, when saidoptical element is formed as a mirror, the wall member is connected viaa joint to an elongated pin that is slideably arranged in a bushing,wherein particularly said bushing is connected to a housing of the lensdevice and/or to said carrier. In this manner the movement/tilting ofthe optical member/wall member can be safely guided.

According to a preferred embodiment of the present invention, the lensdevice further comprises a movement sensor means for sensing an e.g.unintended rapid movement of the lens device that is to be counteracted.The movement sensor means may be designed to detect a yaw movementand/or pitch movement, i.e. a rotation about two orthogonal axes, whichaxes are each orthogonal to the optical axis/axial direction.

According to further preferred embodiment of the present invention, forproviding image stabilization, the lens device comprises a control unitinteracting with said movement sensor means, which control unit isdesigned to control the actuator means depending on a movement to becounteracted sensed by the movement sensor means such that the opticalelement is tilted by the actuator means with respect to the planespanned by the lens shaping member for changing the direction of theincident light beam passing through the lens device in a way thatcounteracts said sensed unintended rapid movement. This is possible,since the unintended movement causes a displacement of a certain imagepoint, e.g. on the surface of the image sensor, which can be compensatedby tilting the optical element and therefore changing the light path ofthe incident light through the lens device such that the same objectpoint is ending up on the same image sensor location as before theunwanted movement and tilting of the lens device.

Preferably, the control unit is designed to control the actuator meanssuch that the actuator means alters the actual spatial position of theoptical element sensed by the position sensor means such that the actualspatial position approaches a reference spatial position of the opticalelement in which the optical element (and therefore the direction of theincident light beam) is tilted such with respect to the lens shapingmember that the unintended rapid movement is counteracted or compensated(see above). Here, alternatively, the actuator means may alter theactual spatial position of the lens shaping member sensed by theposition sensor means (i.e. the optical element rests).

A further aspect of the present invention relates to a method foradjusting a lens device having the features of claim 28, whereinparticularly the method makes use of a lens device according to theinvention.

According to claim 28, the lens device comprises a transparent andelastically expandable membrane, an optical element facing or opposingthe membrane, a wall member, wherein the optical element and themembrane are connected to the wall member such that a volume is formed,a fluid residing in said volume, and a lens shaping member connected toan outside of the membrane, which outside faces away from said volume,and wherein the optical element (or alternatively the lens shapingmember) is tilted with respect to a plane spanned by the lens shapingmember (or with respect to the optical element in case the lens shapingmember is tilted) so as to form the volume into a prism for deflectinglight passing through the volume.

This method may be used for cameras as well as scanners etc.

Preferably, the optical element is moved also in an axial direction withrespect to the lens shaping member (or vice versa), e.g. towards andaway from the lens shaping member) so as to adjust the pressure of thefluid residing inside the volume and therewith a curvature of saidmembrane (particularly so as to adjust the focus of the lens deviceautomatically), wherein said axial direction is oriented perpendicularto said plane (or, as the case may be, to the optical element).

Preferably, the optical element is moved axially by moving the wallmember or plate axially along said axial direction. Preferably, theoptical element is tilted by tilting the wall member or plate withrespect to said plane.

Yet a further aspect of the present invention relates to a method forproviding image stabilization having the features of claim 29, whereinparticularly the method makes use of a lens device according to theinvention.

According to claim 29, the lens device comprises a transparent andelastically expandable membrane, an optical element facing or opposingthe membrane, a wall member, wherein the optical element and themembrane are connected to the wall member such that a volume is formed,a fluid residing in said volume, and a lens shaping member connected toan outside of the membrane, which outside faces away from said volume,wherein an unintended rapid movement of the lens device to becounteracted is sensed (e.g. by a movement sensor means), and wherein anactuator means is controlled (e.g. by a control unit) depending on saidsensed movement to be counteracted such that the optical element istilted by the actuator means with respect to a plane spanned by the lensshaping member (or such that the lens shaper is tilted by the actuatormeans with respect to a plane along which the optical element extends)for changing the direction of the incident light beam passing throughthe lens device in a way that counteracts said sensed movement (see alsoabove). When tilting, the actuator means is preferably designed (orcontrolled) such that the pressure in the fluid is kept constant, sothat the curvature of the membrane is kept constant.

According to a preferred embodiment of this method, particularly forproviding autofocus of the lens device in parallel, particularly at thesame time, the optical element is moved by the actuator means in anaxial direction with respect to the lens shaping member (or vice versa).e.g. towards and away from the lens shaping member, so as to adjust thepressure of the fluid residing inside the volume and therewith acurvature of said membrane, wherein said axial direction is orientedperpendicular to said plane spanned by the lens shaping member.

Preferably, the optical element is moved axially by moving the wallmember or plate axially along said axial direction. Preferably, theoptical element is tilted by tilting the wall member or plate withrespect to said plane.

According to yet another preferred embodiment of the present inventionthe actuator means comprises at least one magnet. The at least onemagnet may comprise a first and a second side which faces away from thefirst side. Particularly, the at least one magnet comprises acircumferential or annular shape, so that the at least one magnetcomprises a continuous recess extending from the first side to saidsecond side of the at least one magnet.

Particularly, the at least one magnet (or the plurality of magnets, seebelow) is magnetized perpendicular to said plane in the axial direction.

Further, the lens device particularly comprises a magnetic flux returnstructure for guiding magnetic flux towards said magnet. Particularly,said return structure (see also above for possible materials) extendsalong the at least one magnet.

In this respect, particularly, the return structure comprises acircumferential or annular shape and particularly extends along or facesthe first side or the second side of the at least one magnet.

Further, particularly, said actuator means comprises at least one coilassociated to said at least one magnet, which at least one coilcomprises a conductor that is wound around a coil axis runningperpendicular to said plane or to said optical element.

Particularly, the coil axis coincides with a cylinder axis of the atleast one magnet or runs parallel to said cylinder axis of the at leastone magnet. Particularly, also the magnetization of the at least onemagnet runs parallel to said coil axis and/or cylinder axis.

Further, according to an embodiment, said coil extends along the atleast one magnet and faces the at least one magnet (wherein said atleast one coil particularly faces the first side or the second side ofthe at least one magnet), so that when a current is applied to the coil,a Lorentz force is generated that causes the at least one magnet and theat least one coil to attract each other or to repel each other dependingon the direction of the current in the at least one coil, particularlyso that the optical element is moved in the axial direction with respectto the lens shaping member (or vice versa: so that the lens shapingmember is moved in the axial direction with respect to the opticalelement, see also above) so as to adjust the pressure of the fluidresiding inside the volume and therewith a curvature of said membrane(said axial direction is oriented perpendicular to a plane along whichthe lens shaping member extends, or along which the optical elementextends, see above), and/or so as to tilt the optical element withrespect to said plane, e.g. the lens shaping member (or vice versa: soas to tilt the lens shaping member with respect to the optical element,see above), particularly so as to form the volume into a prism fordeflecting light passing through the volume.

In the above, said at least one coil can have only one winding directionthroughout. In an embodiment, only one such coil may be present. Thecoil then extends particularly along the associated (e.g. single) magnetfollowing the circumferential or annular course of said magnet andfacing one or the other side of the magnet.

Further, in another embodiment, in order to increase magnetic forces andtheir efficiency. the at least one coil comprises an outer first sectionsurrounding an inner second section of the coil (which second section isconnected in an electrically conducting fashion to the first section),wherein the conductor is wound around said coil axis runningperpendicular to said plane or said optical element such that eachsection of the coil extends along the at least one magnet (which in thisembodiment may be a single magnet) and faces the at least one magnet,wherein in said first section the conductor has a winding direction thatis opposite to the winding direction of the conductor in the secondsection of the coil, so that when a current is applied to the coil, thecurrent flows in one direction in the first section and in the oppositedirection in the second section of the coil, and a Lorentz force isgenerated that either attracts the coil or magnet towards the lensshaping member or pushes the coil or magnet away from the lens shapingmember depending on the direction of the current in said sections of thecoil. Particularly this allows for generating said axial movementbetween the optical element and the lens shaping member described above.

Here, instead of having electrically connected sections of a (single)coil one may also provide two separate coils having opposite windingdirections or currents in opposite directions.

According to a further embodiment, particularly, for tilting the lensshaping member with respect to the optical element or vice versa, aplurality of magnets is provided which are then particularly arrangedaround the axis of the lens device (i.e. around the volume of the lensdevice or along said circumferential return structure). Then,particularly, to each magnet a different coil of a plurality of coils ispreferably associated that faces the respective magnet (e.g. its firstor second side).

In case of such a plurality of magnets, the coils do not need to havesaid first and second section described above. Particularly, each coilhas a particularly elongated and/or curved contour, following a(particularly elongated and/or curved) contour of the associated magnet(e.g. contour of the first or second side of the respective magnet) sothat in one (e.g. outer) half of the coil (which half particularlyextends along the elongated dimension of the coil) the current flows ina first direction along the associated magnet while it flows in theopposite direction in the other (e.g. inner) half of the coil (whichother half particularly also extends along the elongated dimension ofthe coil).

In the above, according to an embodiment, the wall member or at least apart of the wall member may be formed by the at least one magnet. The atleast one magnet (or a plurality of magnets) can be surrounded by aholding material. Particularly the wall member may be formed by a singlemagnet. Particularly, the optical element is then connected to the firstside of the at least one magnet (or wall member). Further, particularly,said membrane is then connected to the second side of the at least onemagnet (wall member). Further, in this embodiment, the return structureis particularly connected to the first side of the at least one magnet(wall member), and the optical element is particularly connected to thefirst side of the at least one magnet (wall member) via said returnstructure.

Further, in this embodiment, the at least one coil or the plurality ofcoils (e.g. when having a plurality of associated magnets but also whenhaving a single associated magnet) is held by a coil frame, particularlyhaving a circumferential or annular shape. Particularly said coil framefaces the at least one (or single) magnet (for instance the second sideof the magnet to which the membrane is attached). Particularly, the lensshaping member is connected, particularly integrally, to the coil frame.

In the above, according to another embodiment, the wall member may bedesigned to hold the at least one coil (or said plurality of coils), sothat particularly the at least one coil surrounds said volume. Further,a position sensor means or feedback sensor, e.g. a Hall sensor, fordetecting the spatial position of the at least one (or single) magnetwith respect to the at least one (or single) coil or vice versa may beconnected to the wall member. Here, particularly, the wall member forms,together with the optical element and the membrane a container (volume)for holding the fluid as well as the at least one coil or the pluralityof coils and eventually said sensor. The coil and wall member can be aprinted circuit board.

Particularly, in this embodiment, the at least one magnet or theplurality of magnets is connected, particularly integrally, to the lensshaping member.

According to a further embodiment, the lens device comprises atemperature sensor that is measuring the temperature of the lens device.The measured temperature can be used to calibrate the lens and make itsoptical power response to the control signal less temperature sensitive.

Further, according to an embodiment of the present invention, a fieldguiding plate is placed such that an attractive force builds up betweenthe at least one (or single) magnet and the field guiding plate, suchthat the force increases when said magnet is moved towards the fieldguiding plate when the lens (e.g. membrane) becomes more deflected.

Further, according to an embodiment, the lens device may be formed as aso-called double liquid lens. Here, the lens device comprises a furthervolume on a side facing away from said volume being filled with saidfluid, wherein the further volume is filled with a further fluid. Themembrane here also delimits one side of said further volume. Theadvantage of such a configuration is the fact, that the further liquidprevents e.g. a vertically extending membrane from becoming deformed dueto gravitation. Embodiments of such lens devices are shown for instancein FIGS. 31 to 36.

Particularly, the lens device according to the invention can be appliedin the following: Lighting fixtures, light shows, printers, medicalequipment, fiber coupling, head worn glasses, laser processing,biometric, metrology, electronic magnifiers, robot cam, fiber coupling,motion tracking, intra-ocular lenses, mobile phones, military, digitalstill cameras, web cams, microscopes, telescopes, endoscopes,binoculars, research, industrial applications, surveillance camera,automotive, projectors, ophthalmic lenses, vision systems, rangefinders, bar code readers.

Further features and advantages of the present inventions as well asembodiments of the present invention shall be described in the followingwith reference to the Figures, wherein

FIGS. 1-3 show schematical cross sectional views of a lens deviceaccording to the invention having a transparent optical element that isoriented parallel to the membrane (FIG. 1) or tilted with respect to themembrane (FIGS. 2 and 3) for deflecting a light beam passing through thevolume of the tunable lens;

FIGS. 4-6 show schematical cross sectional views of the lens deviceshown in FIGS. 1-3 wherein in addition the curvature of the membrane isadjusted by means of a lens shaping member acting on the membrane forfocusing the light beam;

FIGS. 7-9 show schematical cross sectional views of a further lensdevice according to the invention having an optical element in the formof a mirror that is oriented parallel to the membrane (FIG. 1) or tiltedwith respect to the membrane (FIGS. 2 and 3) for deflecting a light beampassing through the volume of the tunable lens;

FIGS. 10-12 show schematical cross sectional views of the lens deviceshown in FIGS. 7-9, wherein in addition the curvature of the membrane isadjusted by means of a lens shaping member acting on the membrane forfocusing the light beam;

FIGS. 13-15 shows cross sectional views of a lens device according tothe invention having a bellows and a transparent optical element;

FIGS. 16-18 show different views of a further lens device according tothe invention having a transparent optical element;

FIG. 19-20 show different views of a further lens device according tothe invention having an optical element in the form of a mirror;

FIG. 21-23 show schematical cross sectional views of magnetic fluxguiding structures that can be used with the magnets of an actuatormeans of a lens device according to the invention;

FIG. 24-26 show schematic views of further actuator means that can beused in the framework of the present invention;

FIG. 27 shows a schematic cross sectional view as well as detail of alens device according to the invention having an actuator means using acoil with two sections facing an annular magnet;

FIG. 28 shows schematical views of the lens device shown in FIG. 27 aswell as a modification of this lens device allowing for tilting of theoptical element;

FIG. 29 shows a schematical view of a lens device as shown in FIG. 28having an additional field guiding plate;

FIG. 30 shows a schematical cross sectional view of a lens deviceaccording to the invention, wherein the lens shaping member is connectedto the magnet of the actuator which moves the magnet with respect to atleast one coil held by a wall member that also holds the fluid with helpof the membrane and the optical element being attached to the wallmember, respectively;

FIG. 31 shows a cross sectional view of a lens device according to theinvention which is a modification of the lens device shown in FIG. 30;

FIG. 32 shows a cross sectional view of a lens device according to theinvention which is a modification of the lens device shown in FIG. 31;

FIG. 33 shows schematical cross sectional views of four different lensdevices according to the invention having two volumes filled with afluid (so called double liquid lenses);

FIG. 34 shows a schematical cross sectional view of a lens device shownin FIG. 33;

FIG. 35 shows a modification of the lens device shown in FIG. 34; and

FIG. 36 shows a schematical cross sectional view of a lens device shownin FIG. 33.

FIGS. 1 to 3 show schematical cross sectional views of a tunable lensdevice 1 according to the invention. The lens device 1 comprises atransparent and elastically expandable membrane 10, a transparent (e.g.planar) optical element 20 facing or opposing the membrane 10, a wallmember 300 in the form of a rectangular plate 300 having a continuouscircular recess 301 formed therein in the center of the plate 300, whichrecess 301 extends from a first side 300 a of the plate 300 to a secondside 300 b of the plate 300, which second side 300 b faces away from thefirst side 300 a. The rigid optical element 20 is connected to the firstside 300 a, whereas said membrane 10 is connected to the second side 300b such that a volume or container V is formed that is at least delimitedby the membrane 10, the optical element 20, and said plate 300. Thevolume V is completely filled with a transparent fluid F. The opticalelement 20, said volume V with the fluid F residing therein and themembrane 10 form a tunable lens. For adjusting the curvature,particularly the focus of this lens, the lens device 1 further comprisesa lens shaping member 11 that is attached to an outside 10 a of themembrane 10, which outside 10 a faces away from said volume V. The lensshaping member 11 thereby delimits an optically active and elasticallyexpandable (e.g. circular) region 10 c of the membrane 10, whereinparticularly said region 10 c extends up to an (e.g. circumferential)inner edge of the lens shaping member 11, and wherein particularly saidregion 10 c comprises said curvature of the membrane 10 to be adjusted.The lens shaping member 11 may be formed as an annular (e.g. circular)frame for generating a spherical tunable lens, but may also have anyother geometry. For instance, a lens shaping member having two parallelopposing linear frame members (i.e. two frame members that face eachother) may be used for generating a tunable cylinder lens.

As shown in FIGS. 1 to 3, the lens device 1 comprises an actuator means40 that is designed to tilt the optical element 20 with respect to aplane spanned by the lens shaping member 11 (i.e. the lens shapingmember 11 defines said fictitious plane or extends in or along saidfictitious plane), which allows one to give the volume V under theoptical element 20 the form of a prism, such that light that passes thevolume V is deflected as indicated in FIGS. 2 and 3. This can beemployed for image stabilization as well as scanning.

When the lens device 1 is used in or as a camera, an image point on thesurface of an image sensor 52 (cf. FIG. 16 for instance) may be shifteddue to an unintended rapid movement of the lens device 1. This can becounteracted by shifting the crossing point between the incident lightbeam A′ associated to an object point and the surface of the imagesensor 52 in the opposite direction. For this, the lens device 1 maycomprise a movement sensor means for sensing said unintended rapidmovement of the lens device 1 to be counteracted, wherein the lensdevice 1 may further comprise a control unit connected to the movementsensor means, which control unit is designed to control the actuatormeans 40 depending on the movement to be counteracted sensed by themovement sensor means such that the optical element 20 is tilted by theactuator means 40 with respect to said plane spanned by the lens shapingmember 11 (i.e. along which plane the lens shaping member extends) forchanging the course of the incident light beam A′ associated to anobject point in a way that counteracts said sensed movement, i.e., theshift of an image point on the surface of an image sensor (or imageplane) due to a rapid and unintended movement of the lens device 1 iscompensated by a shift of the crossing point of said incident light beamA′ associated to an object point and the image sensor (image plane) inthe opposite direction.

As shown in FIGS. 4 to 6 the lens device 1 according to the invention isfurther capable of deforming the membrane 10 at the same time bypressing with the lens shaping member 11 against the membrane 10. Thiscan be achieved by means of the same actuator means 40 that is alsodesigned to move the optical element 20 in an axial direction A (beingoriented perpendicular to the plane spanned/defined by the lens shapingmember 11) with respect to the lens shaping member 11 so as to adjustthe pressure of the fluid F residing inside the volume V and therewith acurvature of said membrane 10 (see also above). This particularly allowsone to change the curvature between two different convex curvatures, ortwo different concave curvatures, or even between a convex and a concavecurvature. Thus, the focus of the tunable lens can be altered veryeffectively. Preferably, the actuator means 40 is designed to act on thewall member 300 for moving the optical element 20 axially as well as fortilting the optical element 20 with respect to the fixed lens shapingmember 11.

FIGS. 7 to 9 also show tilting movements of a lens device 1 according tothe invention, wherein, in contrast to FIGS. 1 to 6, the lens device 1now comprises an optical element 20 in form of a mirror that has areflecting surface that faces the volume V of the tunable lens. Here,tilting of the optical element 20 allows for scanning a 2D image plane.

As shown in FIGS. 10 to 12 this can also be combined with deforming themembrane 10 for adjusting the focus of the tunable lens as discussedbefore with respect to FIGS. 4 to 6 such that 3D scanning is possible.

FIGS. 13 to 15 show a lens device 1 of the kind shown in FIGS. 1 to 6,which may form part of a camera, particularly of a camera of a mobilephone. Said device 1 comprises in addition a circumferential bellows 30which connects the lens shaping member 11 that is attached to theoutside 10 a of the membrane 10 thus defining said region 10 c to thesecond side 300 b of the plate 300 adjacent to the recess 301 of theplate 300. The bellows 30 has two circumferential regions 31 extendingalong the lens shaping member 11 as shown in FIG. 13, which regions 31are connected to each other via a circumferential crease 32 extendingalong said lens shaping member 11. This allows for a contracting andprolonging the bellows 30 along the axial direction A and thereforeallows for a pronounced tilting movement/axial movement of the plate300/optical element 20. A contracted bellows 30 due to an axial movementof the plate 300 towards the lens shaping member 11 is shown in FIG. 14.As a consequence said region 10 c of the membrane 10 develops apronounced convex bulge. A more elongated state of the bellows 30 isshown in FIG. 13 leading to a flat region 10 c of the membrane 10.Further, FIG. 15 shows a tilted plate 300/optical element 20 incombination with a convex bulge of the region 10 c of the membrane 10due to an axial movement of the plate 300/optical element 20 towards thelens shaping member 11.

As indicated in FIGS. 13 to 15 the lens shaping member 11 is furtherconnected to a carrier 50, which faces the second side 300 b of theplate 300. Said carrier 50 may comprise or may be formed as an opticalassembly such as a lens stack 51 and/or an image sensor 52 (cf. FIG.16). Thus the lens shaping member 11 is fixed and axial movement andtilting of the optical element 20 with respect to the lens shapingmember 11 is accomplished by merely axially moving/tilting the plate 300by means of said actuator means 40.

As can be seen from FIGS. 10 to 13, the actuator means 40 comprises fourelectrically conducting coils 41 being integrated into the plate 300along the circular recess 301, wherein each coil 41 is equally spacedfrom its two neighboring coils 41 along the circular recess 301.

The actuator means 40 further comprises four magnets 42, wherein eachmagnet 42 is associated to one of the coils 41, wherein said magnets 42are connected to the carrier 50 and arranged adjacent to the associatedcoil 41, wherein the respective magnet 42 is arranged radially fartheroutward than the associated coil 41.

Said magnets 42 are designed to interact with the respectivelyassociated coils 41 such that when a current is applied to a coil 41,the respective coil 41 is either moved towards the carrier 50 or awayfrom the carrier 50 depending on the direction of the respectivecurrent.

Further, as shown in FIG. 12 to 15, for guiding the magnetic flux of themagnets 42, a magnetic flux guiding structure 70 is provided for eachmagnet 42, wherein each magnetic flux guiding structure 70 comprises, asshown in FIG. 21 a first arm 72 extending along the axial direction Aand an opposing parallel second arm 74 (i.e. arm 72 faces arm 74) beingconnected to the first arm via a third arm 73 of the structure 70, whichthird arm 73 extends perpendicular to the axial direction A and connectsa lower end of the first arm 72 to a lower end of the second arm 74. Thestructure 70 further comprises an end region 71 of the second arm 74,wherein each of the four end regions 71 protrudes through an associatedaperture 302 formed in the plate 300 as well as into or through therespective associated coil 41. The magnets 42 are arranged adjacent tothe respective first arm 72 such that the magnetization of therespective magnet 42 points towards the second arm 74 and such that therespective magnet 42 is arranged between the respective first arm 72 andthe respective coil 41.

As shown in FIGS. 22 and 23, other magnetic flux guiding structures 70are also possible. FIG. 22 shows a further structure 70 with twoopposing magnets 42, 42′ (i.e. magnet 42 faces magnet 42′) which is amodification of the structure 70 shown in FIG. 21. In FIG. 22, the thirdarm 73 further extends towards a fourth arm 75 running parallel to thefirst arm 72 and to the second arm 74, wherein the second arm 74 nowprotrudes from the center of the third arm 73 and is arranged betweenthe first and the fourth arm 72, 75. The further magnet 42′ is arrangedadjacent to the fourth arm 75 and between the fourth arm 75 and thesecond arm 74, wherein the magnetization of the further magnet 42 pointstowards the second arm 74.

Further, the structure 70 shown in FIG. 23 is a modification of thestructure 70 shown in FIG. 21. In FIG. 23, the magnet 42 is arranged onthe third arm 73, wherein said end region 71 that receives theassociated coil 41 is arranged on top of the magnet 42, wherein themagnetization of the magnet 42 now points towards said end region 71 ofthe structure 70.

In order to detect the actual spatial position of the optical element20/plate 300, the lens device 1 comprises a position sensor means 60.This sensor means 60 can be formed as a hall sensor 62 that is arrangedon the plate 300, particularly on the second side 300 b of the plate 300and senses an associated signal magnet 61 connected to the carrier 50,which signal magnet 61 faces or opposes its associated hall sensor 62.Particularly, the respective signal magnet 61 is arranged radiallyoutward relative to the associated hall sensor 62.

The lens device 1 may comprise for such pairs of hall sensors 62 andsignal magnets 61, wherein the signal magnets 61 are equally spacedalong the periphery of the carrier 50. Likewise, the hall sensors 62 areequally spaced along the periphery of the plate 300.

Of course, also other position sensor means can be employed such ascapacitive sensors, magneto-resistive sensors, or strain sensors.

FIGS. 16 to 18 show a further lens device 1, which may form part ofcamera, particularly of a camera of a mobile phone. The lens device 1 isdesigned as described with respect to FIG. 13 to 15 with the differencethat the bellows 30 is now omitted. Here, the membrane 10 is directlyattached to the second side 300 b of the plate 300 as can be seen fromFIG. 17, for instance.

As Indicated in FIG. 16, electrical connections to the coils 41 and/orposition sensor means 62 on the plate 300 may be made by means offlexible wires 80, which provides a way for measuring the spatialposition of the optical element 20/plate 300 by means of strain sensors,wherein such a strain sensor is attached to each flexible wire 80. Incase the spatial position of the plate 300 is altered by means of theactuator means 40 (see above), the flexible wires 80 will be deformedwhich can be detected by means of said strain sensors.

Finally FIGS. 19 and 20 show a further lens device 1 according to theinvention which is constructed as described with respect to FIGS. 16 to19 with the difference that the optical element 20 is now formed as amirror having a reflecting surface that faces the volume V of thetunable lens. Further, in contrast to FIGS. 16 to 19, the coils 41 arearranged on the first side 300 a of the plate 300.

The lens device 1 shown in FIGS. 19 to 20 may form part of a 3D scannerfor scanning images. In order to safely guide the movement of the plate300 which has already been described above, the plate 300 is connectedvia a joint 93 in the form of a ball bearing to an elongated pin 91 thatis slidably arranged in a bushing 90. Preferably, the bushing 90 isconnected to a housing of the lens device 1 and/or to said carrier 50.Further electrical connections to the plate 300 are preferably made bymeans of four flexible wires 92 which extend from the wall member 300,particularly from the coils 41. The flexible wires 92 comprise someslack so that they do not interfere with a movement of the plate 300.Preferably, the flexible wires 92 extend from the plate 300 towards thebushing 90 where they are fastened to the bushing 90.

A further embodiment of an actuator means that can be used to axiallymove and/or tilt the plate 300/optical element 20 of the lens device 1is shown in FIG. 24. According thereto the actuator means comprises aplurality, particularly, two, three or four, electrically conductingcoils 41 rigidly connected to the carrier 50. Preferably, the coils 41are each arranged adjacent to an associated magnetic flux returnstructure 700 (e.g. out of a magnetically soft material such as e.g.steel). The magnetic flux return structure 700 may comprise regions 720,730 extending laterally on either side of the respective coil 41 as wellas a region 710 protruding into the respective coil 41. A modificationis shown in FIG. 25 where each magnetic flux return structure 700 has aregion 720 extending laterally, namely radially farther inward than therespective coil 41, as well as a region 710 protruding into therespective coil 41. Here, each coil 41 has a region protruding beyondthe plate 300 in the extension plane of the plate 300 which respectiveregion of the coil 41 is not flanked by a region of the returnstructure.

The actuator means further comprises a corresponding plurality ofmagnetic flux guiding structures 740 arranged in or on the plate 300,wherein each magnetic flux guiding structure 740 is associated to adifferent coil 41, and faces or opposes the respective coil 41/magneticreturn structure 700 such that a gap is present between the respectivereturn structure 700/coil 41 on one side and the associated magneticflux guiding structure 740 on the other side. The plurality of magneticflux guiding structures 740 can also be made out of one magneticallysoft part. The same is true for the return structure 700. I.e. there mayalso be a single magnetic flux guiding structure facing or opposing thecoils which are arranged adjacent a single magnetic flux returnstructure 700.

When a current now flows through the coils 41, the magnetic flux isguided through the respective return structure 700 and the respectiveflux guiding structure 740. Since the system wants to reduce themagnetic resistance, the respective magnetic flux guiding structure 740will be attracted to the associated return structure 700 to reduce thegap between the two magnetically soft structures and to reduce theresistance for the magnetic flux. Thus, the plate 300 and opticalelement 20 are moved. Depending on the current in the respective coil 41this allows one to move the plate 300 axially along said axial directionand/or to tilt the plate 300 with respect to the plane spanned/definedby the lens shaping member 11. Such an actuator means is also denoted asreluctance actuator.

This embodiment of an actuator means has the advantage that the coil 41and the Hall sensor 62 can be mounted on the carrier 50 (cf. for exampleFIG. 16), i.e., at a fixed position with respect to the lens barrel ofthe fixed optics 51 and no flex connection 80 is required. Furthermore,less components are required. In this case, the signal magnet 61 wouldbe attached to the moveable/tiltable plate 300 that comprises or isformed by the flux guiding structures 740. Furthermore, no permanentmagnets (except for the Hall sensor) are required. The drawback is thatonly attractive forces are possible. Furthermore, the Hall sensor can bereplaced by directly sensing the variable reluctance of the reluctanceactuator, associated to the changing gap between the flux guidingstructure 740 and the return structure 700.

According to yet another embodiment of an actuator means that can beemployed to axially move and/or tilt the plate 30/optical element 20 asshown in FIG. 26, the actuator means may comprise a plurality of first(top) electrodes 810, particularly, two, three or four, arranged in oron the plate 300, as well as a corresponding plurality of secondelectrodes 800 rigidly connected to the carrier 50, wherein each firstelectrode 810 is associated to a different second electrode 800 andfaces or opposes the respective second electrode 800 so that a gap ispresent between the respectively associated electrodes 810, 800. Byapplying a voltage between the respective first and second electrodes810, 800, the plate 300/optical element 20 can be axially moved and ortilted with respect to said plane spanned/defined by the lens shapingmember 11. Thus, besides a magnetic actuation, also an electrostaticactuation is possible. Furthermore, the actuator electrodes 810, 800 canbe used to sense the distance between the electrodes by reading out thecapacitance value between the electrodes.

FIG. 27 shows a schematical cross sectional view of a further tunablelens device 1 according to the invention. As before, the lens device 1comprises a transparent and elastically expandable membrane 10, atransparent (e.g. planar) optical element 20 facing or opposing themembrane 10, a wall member 300 in the form of an annular magnet 300having a continuous circular recess 301 formed therein in the center ofthe magnet 300, which recess 301 extends from a first side 300 a of themagnet 300 to a second side 300 b of the magnet 300, wherein the secondside 300 b of the magnet faces away from its first side 300 a.Furthermore, the magnet 300 is axially magnetized (in the axialdirection A). The rigid optical element 20 is connected to the firstside 300 a of the magnet 300 via a plate-like annular magnetic fluxreturn structure 305 that serves for guiding returning magnetic fluxback to the magnet 300 and that is positioned between the opticalelement 20 and the magnet 300. Said membrane 10 is connected to thesecond side 300 b of the magnet such that a volume or container V isformed that is at least delimited by the membrane 10, the opticalelement 20, said magnet 300 forming a circumferential wall member 300 ofsaid container, and the return structure 305 (which also forms part ofthe container wall). As described before, the volume V is completelyfilled with a transparent fluid F. The optical element 20, said volume Vwith the fluid F residing therein and the membrane 10 form a tunablelens. For adjusting the curvature, particularly the focus of this lens,the lens device 1 further comprises a lens shaping member 11 that isattached to an outside 10 a of the membrane 10, which outside 10 a facesaway from said volume V. The lens shaping member 11 thereby delimits anoptically active and elastically expandable (e.g. circular) region 10 cof the membrane 10, wherein particularly said region 10 c extends up toan (e.g. circumferential) inner edge of the lens shaping member 11, andwherein particularly said region 10 c comprises said curvature of themembrane 10 to be adjusted. The lens shaping member 11 may be formed asan annular (e.g. circular) frame for generating a spherical tunablelens, but may also have any other geometry (see above).

Further, the lens device 1 comprises an actuator means 40 that is shownin the detail on the right hand side of FIG. 27. Said actuator means 40is designed to generate an axial movement of the optical element withrespect to an axial direction A running perpendicular to the planedefined by the lens shaping member 11. Thus, the lens device 1 may beused in an autofocus application where the focus of the lens (i.e. thecurvature of the membrane 10) may be controlled as described before bymoving the optical element 20 with respect to the lens shaping member 11in the axial direction.

For this, besides said magnet 300, the actuator device 40 comprises acoil 400 that is carried by an annular coil frame 406 that faces thesecond side 300 b of the magnet 300 and is coaxially arranged withrespect to the magnet 300. The lens shaper 11 is connected to the coilframe 406, particularly integrally, and protrudes from the coil frame406 towards the membrane 10 so as to contact it as described above.Further, the coil frame 406 surrounds a recess being aligned with therecess 301 of the magnet 300, so that light can pass the volume V andthe coil frame 406 in the axial direction A.

As shown in FIG. 28, particularly on the lower left hand side, the coil400 extends circumferentially in the coil frame 406 and also extendsalong the magnet 300 (coaxially with the magnet 300) and faces thesecond side 300 b of the latter so that the magnet 300 is arrangedbetween the coil 400 and the magnetic flux return structure 305.

Further, in the embodiment shown in FIG. 27 and in the lower left handside of FIG. 28 as well as in the upper left hand side of FIG. 28, thecoil 400 comprises a conductor that is wound around a coil axis thatcoincides with the axial direction A (i.e. runs perpendicular to saidplane or to said lens shaping member 11), wherein the coil 400 comprisesan outer first section 401 surrounding an inner second section 402 ofthe coil 400, wherein the conductor is wound around said coil axis suchthat each of said two sections 401, 402 of the coil 400 extends alongthe magnet 300 and faces the second side 300 b of the magnet 300. Now,as indicated in FIG. 28 on the lower left hand side, in said firstsection 401 the conductor has a winding direction that is opposite tothe winding direction of the conductor in the second section 402 of thecoil 400, so that when a current is applied to the coil 400, the currentflows in one direction in the first section 401 (out of the plane ofprojection) and in the opposite direction in the second section 402(Into the plane of projection) of the coil 400. This generates a Lorentzforce that causes the magnet 300 and the coil 400 to attract each otheror to repel each other in a very efficient manner as indicated on theright hand side of FIG. 27, depending on the direction of the current insaid sections 401, 402 of the coil 400. By means of such a magnet-coilconfiguration, the optical element 20 can be moved towards and away fromthe lens shaping member 11 in the axial direction A, i.e. for increasingthe curvature of the membrane 10 so as to alter the focus of the lens asindicated in FIG. 28 in the upper middle panel for instance.

A modification of this magnet-coil configuration is shown on the lowerright hand side of FIG. 28. This modification also allows to—besidesmoving the optical element axially as it is needed for instance when thelens device 1 is used as an autofocus lens—to tilt the optical element20 with respect to said plane (i.e. the lens shaping member 11). In thismodification, instead of a single magnet 300, the actuator means 40 ofthe lens device 1 comprises a plurality of magnets 303, e.g. threemagnets 303 as shown on the lower right hand side of FIG. 28, which arearranged along the annular return structure 305, namely around thevolume V, so that they are e.g. evenly spaced along the periphery of thereturn structure 305 or volume V (or in other words arranged around thecentral axis A of the optical device 1). All three magnets 303 aremagnetized in the axial direction A. Here, each magnet 303 comprises afirst and a second side 303 a, 303 b which second side 303 b faces awayfrom the first side 303 a, wherein the return structure 305 is connectedto the first side 300 a while the membrane 10 is attached to the secondsides 303 b of the magnets 303. The magnets 303 may be embedded into thereturn structure 305 or the latter may simply be connected to the firstsides 303 a of the magnets 303. The magnets 303 form part of a wallmember 300 that surrounds the fluid filled volume V of the lens. Asindicated on the lower right hand side of FIG. 28, the second sides 303b of the magnets 303 may further each comprise a certain contour such asan elongated curved contour which follows the contour of a section ofthe annular (circular) return structure 305 to which the respectivemagnet 303 is attached.

Now, instead of a single coil 400, the lens device 1 comprises aplurality of coils 403 (here e.g. three coils 403) corresponding to thenumber of magnets 303, wherein each coil 403 of the plurality of coilsis associated to a different magnet 303, wherein the respective coil 403faces the associated magnet 303 in the axial direction A.

Particularly, each of said coils 403 comprises an outer contour thatmimics the contour of the second side 303 b of the associated magnet303, e.g., each coil may comprise an elongated, curved contour, so thatin an outer half 403 a of the respective coil 403 the current flows in afirst direction along the associated magnet 303 while it flows in theopposite direction in the other inner half 403 b of the respective coil403. Thus, when a current is applied to one of the coils 403, a Lorentzforce is generated that causes the associated magnet 303 and said coil403 to attract each other or to repel each other depending on thedirection of the current in said coil 403. This allows to tilt theoptical element 20 with respect to a plane spanned by the lens shapingmember 11 or with respect to the lens shaping member 11 itself, whichallows one to give the volume V under the optical element 20 the form ofa prism, such that light that passes the volume V is deflected asindicated in FIG. 28 in the upper right hand panel. This can be employede.g. for image stabilization as described above. Of course, in case allcoils 403 are actuated in a symmetric fashion, the curvature of themembrane 10 can be altered in addition due to an axial movement of theoptical element 20 with respect to the lens shaping member 11 so that anautofocus function can be combined with image stabilization.

Unless not stated otherwise, the above described magnet-coilconfigurations (single coil and single magnet as well as multiple coilsand magnets) can both be applied to the embodiments that will bedescribed below. Furthermore, it is also possible to have aconfiguration with a single magnet and multiple coils.

FIG. 29 shows a modification of the embodiments shown in FIGS. 27 and28, wherein in addition to these embodiments, the lens device 1according to FIG. 29 comprises an annular field guiding plate 407 thatis arranged coaxially with respect to the coil frame 406 on a side ofthe coil frame 406 that faces away from the magnet 300. When the magnet300 is moving down towards the coil 400 due to the Lorenz force createdby a current through the coil 400, the magnet 300 starts to getattracted more and more to the field guiding plate 407. This attractiveforce helps to deform the membrane 10, supporting the Lorenz force andtherefore makes the lens device 1 more efficient. Furthermore, the fieldguiding plate 407 also helps to magnetically shield the device 1.

FIG. 30 shows a further lens device 1 according to the invention. Here,in contrast to FIGS. 27 to 29, the annular magnet 300 to which firstside 300 a the return structure 305 is connected is connected to thelens shaping member 11 which protrudes downwards from the magnet 300towards the membrane 10 and contacts the membrane 10 from above, whichmembrane 10 in turn is connected to a circumferential wall member 406which also carries the coil 400 (or coils 403) that face the second side300 b of the magnet 300. Here, the circumferential wall member 406together with the membrane 10 and the optical element 20 which isconnected to or an integral part of the wall member 406 (e.g. amulti-layer printed circuit board) on a side facing away from the sideof the wall member 406 to which the membrane 10 is connected, form acontainer of volume V for the fluid F. For detecting a movement of themagnet 300 that may be used for controlling the actuator means 40 asdescribed above, a Hall sensor 408 is provided that may be arranged onthe wall member 406. In the embodiment shown in FIG. 29, the magnet 300and the lens shaping member 11 connected thereto is axially moved and/ortiled by the actuator means with respect to the optical element 20 asdescribed above, while in FIGS. 27 to 29 it is the other way around.

FIG. 31 shows a modification of the embodiment shown in FIG. 30, whereinin contrast to FIG. 30, the coil 400, being a coil of uniform windingdirection, is arranged on the first side 300 a of the annular magnet300, while the return structure is arranged on the second side 300 b ofthe magnet 300. Here, the coil 400 is connected to the return structure305 via an axially extending spacer 409 that surrounds the magnet 300.

Further, FIG. 32 shows a modification of the embodiment shown in FIG.31, wherein the return structure 305 is omitted and the lens shapingmember 11 is formed by the annular magnet 300 itself.

FIG. 33 shows four different ways of arranging magnets 300 and coils 400with respect to the membrane 10 in a configuration with one deformablemembrane 10 and two liquid volumes V, V′. By selecting two liquids F, F′with different refractive indices but similar density, a gravityinsensitive lens can be built.

FIG. 34 shows the configuration shown in FIG. 33 on the lower left handside in detail. Here, the membrane 10 is arranged between an annular toplens shaping member 11 a contacting the membrane 10 from above and an(e.g. identical) bottom lens shaping member 11 b contacting the membrane10 from below. The membrane 10 is further held between a circumferentialtop spacer 410 and a circumferential bottom spacer 411, wherein anoptical element 20 in form of a transparent top glass 20 is connected tothe top spacer 410, so that the top spacer 410, the top glass 20, andthe membrane 10 form a (top) volume V being filled with a (top) fluid F,and wherein a further optical element 21 in the form of a transparentbottom glass 21 is connected to the bottom spacer 411, so that thebottom spacer 411, the bottom glass 21, and the membrane 10 form a(bottom) volume V being filled with a (bottom) fluid F′. Now, In orderto deform the membrane 10 according to the principles described above,the top lens shaping member 11 a is connected to an annular top magnet300 residing in the volume V, and the bottom lens shaping member 11 b isconnected to an annular bottom magnet 300′ that faces the top magnet 300in the axial direction A and is arranged coaxially with respect to thetop magnet 300, wherein the two lens shaping members 11 a, 11 b arearranged between the two magnets 300, 300′ in the axial direction A.Furthermore, the two magnets 300, 300′ are axially magnetized (in theaxial direction A). Here, each of the magnets 300, 300′ can be actuatedwith an associated coil, namely top coil 400, and bottom coil 400′,which may each be arranged on or embedded into a printed circuit board(PCB), wherein the top coil 400 associated to the top magnet 300 may bearranged on the top glass 20 so that it faces the top magnet 300, andwherein the bottom coil 400′ associated to the bottom magnet 300′ can bearranged on the bottom glass 21 so that it faces the bottom magnet 300′.Particularly, the magnets 300, 300′ and associated coils 400, 400′ canbe configured as described above with respect to FIGS. 27 and 28. Incase the top and bottom coil 400, 400′ are connected such that bothcoils 400, 400′ cause the magnets 300, 300′ to move up or down, a veryefficient actuation of the magnets can be achieved.

Further, FIG. 35 shows a modification of the embodiment shown in FIG.34, wherein in contrast to FIG. 34, the top magnet 300, top lens shapingmember 11 a and the top coil 400 are omitted.

FIG. 36 shows the configuration shown on the lower left hand side ofFIG. 33 in detail. Here, the annular lens shaping member 11 contactingthe membrane 10 from above also functions as a coil frame for carryingthe coil 400 which is embedded into the lens shaping member 11. In orderto provide electrical connections to the coil(s) 400, the lens shapingmember 11 is connected to a contact spring 412 via which the lensshaping member is connected to a circumferential top spacer 410 and to acircumferential bottom spacer 411. Further, in the axial direction A,the lens shaping member/coil frame 11 is arranged between an annular topmagnet 300 and an annular bottom magnet 300′, wherein the top magnet 300is connected to a top return structure 305 which in turn is connected toa top glass 20 that is connected to the top spacer 410, and wherein thebottom magnet 300′ is connected to a bottom return structure 305′ whichin turn is connected to a bottom glass 21 that is connected to thebottom spacer 411. The top magnet 300 and bottom magnet 300′ are bothmagnetized in the axial direction A. Now, a circumferential deformabletop wall (e.g. In the form of a top bellows) 413 extends from the topmagnet 300 towards the lens shaping member 11 so that a top volume V isformed that is filled with a top fluid F and that is delimited by thetop glass 21, the top bellows 413 and the membrane 10. Likewise, acircumferential deformable bottom wall (e.g. in the form of a bottombellows) 414 extends from the bottom magnet 300′ towards the lensshaping member 11 so that a bottom volume V′ is formed that is filledwith a bottom fluid F′ and that is delimited by the bottom glass 21, thebottom bellows 414 and the membrane 10.

In the embodiments having two volumes V, V and fluids F, F′ therein, thefluids can be different in refractive index but similar in density.Particularly, the further (bottom) fluid F′ can be one of the fluidsdescribed above. The particular advantage of having two fluid-filledvolumes and a membrane 10 there between is the fact that gravity inducedcoma can be almost completely removed and the lens is much less shocksensitive.

Also here, the lens shaping member 11 can be moved to deform themembrane 11 using the coil 400 and the magnets 300, 300′ according toprinciples described above.

Finally, the embodiments shown on the upper left hand side and the upperright hand side of FIG. 33 are modifications of the embodiment shown inFIG. 34, wherein the embodiment shown on the upper left hand side ofFIG. 33 corresponds to the embodiment of FIG. 34 with the difference,that the top coil 400 is arranged in the top volume V adjacent to thetop glass 20, and the bottom coil 400′ Is arranged in the bottom volumeadjacent the bottom glass 21. Further, the embodiment shown in FIG. 33in the upper right hand side corresponds to the embodiment shown in theupper left hand side, but now the top coil has changed position with thetop magnet, while the bottom coil has changed position with the bottommagnet.

The invention claimed is:
 1. An actuator comprising: an electricallyconducting coil arranged on or integrated into a wall member, whereinthe electrically conducting coil is arranged adjacent to a magnetic fluxreturn structure; a magnet connected to a carrier, wherein the magnetinteracts with the electrically conducting coil such that when a currentis applied to the coil the coil is either moved towards the carrieralong an axial direction or away from the carrier along the axialdirection depending on a direction of the current within the coil; and amagnetic flux guiding structure connected to the carrier, whereinmagnetic flux is guided through the flux return structure and the fluxguiding structure.
 2. The actuator according to claim 1, wherein themagnetic flux return structure is made out of a magnetically softmaterial.
 3. The actuator according to claim 2, wherein the magneticallysoft material is steel.
 4. The actuator according to claim 1, whereinthe actuator is a reluctance actuator.
 5. The actuator according toclaim 4, wherein the actuator is arranged to detect the spatial positionof the wall member.
 6. The actuator according to claim 5, wherein theactuator directly senses a reluctance of the reluctance actuatorassociated to a gap between the magnetic flux guiding structure and theflux return structure.
 7. The actuator according to claim 5, furthercomprising a position sensor using a high frequency current signal formeasuring a spatial position of the wall member via the electricallyconducting coil.
 8. The actuator according to claim 6, furthercomprising a position sensor using a high frequency current signal formeasuring a spatial position of the wall member via the electricallyconducting coil.
 9. The actuator according to claim 1, wherein themagnet comprises a first magnet and a second magnet connected to thecarrier, wherein the first magnet is associated with the electricallyconducting coil.
 10. The actuator according to claim 9, furthercomprising a second electrically conducting coil, wherein the secondmagnet is associated to the second electrically conducting coil.
 11. Theactuator according to claim 10, further comprising an optical element,wherein the first magnet and the second magnet is each magnetizedperpendicular with respect to a plane along which the optical elementextends.
 12. The actuator according to claim 10, wherein the firstmagnet and the second magnet are each magnetized in an identicaldirection.
 13. The actuator according to claim 11, wherein theelectrically conducting coil comprises a conductor that is wound arounda coil axis running perpendicular to the plane, the coil axis coincideswith a cylinder axis of the first magnet, and the magnetization of thefirst magnet runs parallel to said coil axis and/or cylinder axis. 14.The actuator according to claim 11, wherein the electrically conductingcoil comprises a conductor that is wound around a coil axis runningperpendicular to the plane the coil axis runs parallel to the cylinderaxis of the first magnet of the plurality of magnets, and themagnetization of the first magnet runs parallel to the coil axis and/orcylinder axis.
 15. The actuator according to claim 1, wherein theelectrically conducting coil is embedded into a printed circuit board.16. The actuator according to claim 1, wherein the wall member comprisesa recess, and the electrically conducting coil is arranged along therecess.
 17. The actuator according to claim 16, further comprising asecond electrically conducting coil and a third electrically conductingcoil, wherein the electrically conducting coil is equally spaced fromthe second electrically conducting coil and the third electricallyconducting coil along the recess.
 18. The actuator according to claim 1,wherein the magnetic flux guiding structure faces or opposes theelectrically conducting coil.
 19. The actuator according to claim 1,wherein the magnetic flux return structure is adjacent to theelectrically conducting coil.
 20. The actuator according to claim 1,wherein the magnetic flux return structure comprises regions extendinglaterally on either side of the electrically conducting coil as well asa region protruding info the electrically conducting coil.
 21. Theactuator according to claim 1, wherein the electrically conducting coilextends along the magnet and faces a side of the magnet, so that when acurrent is applied to the electrically conducting coil, a Lorentz forceis generated that causes the magnet and the electrically conducting coilto attract each other or to repel each other depending on a direction ofthe current in the electrically conducting coil.
 22. The actuatoraccording to claim 21, wherein the electrically conducting coilcomprises an outer contour that mimics a contour of the side of themagnet.